Brother FAX-2820 Service Manual page 59

3. The laser beams reflected by the reflection mirror go straight toward the exposure drum below
it, then expose the exposure drum.
The area exposed to the laser beam is the image to be printed. The surface potential of the
exposed area is reduced, forming the electrostatic image to be printed.
Surface
potential (V)
+897
+400
+150
Drum
0
sleeve
Developing
Developing causes the toner to be attracted to the electrostatic image on the drum so as to
transform it into a visible image.
The developer consists of a non-magnetic toner. The developer roller is made of conductive
rubber and the supply roller (which is also made of conductive sponge) rotate against each other.
The toner is charged and carried from the supply roller to the developer roller. The toner adheres
to the developer roller and is conveyed to the exposure drum at an even thickness controlled by the
blade. The toner is nipped between the developer roller and the drum and developed onto the
latent image on the drum. The electrostatic field between the drum and the developer roller, which
is DC-biased from the high-voltage power supply, creates the electrostatic potential to attract toner
particles from the developer roller to the latent image area on the drum surface.
Exposure drum
Corona wire
1 Cycle of drum
1 2 3
(a)
(b)
Time
Blade
Developer roller
Transfer roller
3 - 1 4
1 Primary charging
2 Laser beam exposure and developing
(a) Unexposed area
(b) Exposed area
3 Transfer the image to paper
Supply roller
(Non image area)
(Image area)
Confidential